In the operation of an electrostatic deflection inkjet printer, a continuous jet of ink is formed. Electric charges are trapped on some or all of the drops of ink, and an electrostatic field deflects the drops so that the printer prints the desired printed pattern. Drops of ink which are not required for printing are caught by a gutter and are returned to an ink tank within the main body of the printer. The ink includes a solvent which is normally highly volatile so that the drops of ink dry quickly after printing. The solvent also tends to evaporate from the ink that is caught in the gutter and returned to the ink tank, so that the ink used by the printer loses solvent over time. In order to maintain the correct ink viscosity, additional solvent is added from time to time. Additionally, the ink is slowly used up as the printer prints and therefore the ink in the ink tank needs to be replenished. In order to stop and start the ink jet, and perform other operations such as adding ink and solvent and sucking air into the ink gun used to form the ink jet, and to apply or withdraw suction from the gutter, various valves are required within the ink system. The valves are normally electrically controlled and are typically solenoid valves. The ink system will also normally include other electrical components, such as an ink pump for pressurising the ink and a pressure sensor.
The solvents used for the ink are normally highly volatile. WO 2014/156298 proposes that the control components of the printer should be in a separate enclosure from the liquid circulation components so that heat generated in the control components has less effect on the liquid circulation components. The solvents are also often flammable, such as acetone and ethanol. In order to minimise the fire risk arising from solvent vapour within the main body of the printer, it is known for the main printer body to contain a vapour barrier that separates the ink system from the main electrical components. However, as noted above, the ink system itself includes the valves and other electrical components and these need to be connected to the main electrical system in order to operate. The electrical components in the ink system may need to be double-insulated for safety, and the wiring connecting these components to the main electrical system has to pass through the vapour barrier. The portion of each wire that is on the ink system side of the vapour barrier may also need to be double insulated for safety. These double insulated wires tend to be thicker than normally insulated wires and are also stiffer. This makes it difficult to work with these wires when assembling the printer and they cannot necessarily bend as sharply as normal wires when they are routed from the vapour barrier to the place where they are connected to the relevant component in the ink system.